Process control valves are widely used in chemical processing plants. As shown in FIG. 1, a conventional process control valve 10 operates to selectively permit fluid flow between an inlet 12 and an outlet 14 along a flow path. A plug 16 opens or closes the valve 10 by translating axially within a guiding sleeve 20 between a closed position and an open position. In the closed position, a head 18 of the plug 16 blocks a narrowing aperture 22 and engages a valve seat 26 to block the flow path, preventing flow through the valve 10. In the open position, the head 18 of the plug 16 is positioned away from the narrowing aperture 22 and the valve seat 26. In the open position, flow passes through a cylindrical channel 24 defining the narrowing aperture 22 and through the outlet 14. A user pushes or pulls a valve stem 28 to move the valve plug 16 axially within the sleeve 20.
Process control valves 10 are sometimes used to selectively permit the flow of slurries including dense process materials. The dense process materials within the slurry tend to build up and cause clogging along various places in the flow path and around the plug 16. In the ethanol production process, for example, sugarcane bagasse is processed and transported through a processing facility. A number of process control valves are positioned in the flow path of the bagasse to selectively permit bagasse movement. The fibrous nature of bagasse causes build-ups of material to occur within the valve 10 along the guiding surfaces of the plug 16 or sleeve 20 and in a gap 30 above the plug 16. The build-ups of material decrease the clearance between the plug 16 and the sleeve 20 and increase the friction experienced by the plug 16 when an operator attempts to close or open the process control valve 10. At times, the material buildup becomes so substantial that the plug 16 becomes completely stuck in one position or cannot open fully, and the valve 10 cannot operate properly. A lengthy operational shutdown and maintenance procedure to clean the plug 16 and sleeve 20 must then be performed.